Overview

In the last chapter, we introduced the overall configuration and hardware components for a voice over WLAN system. While the handset might be the visible element of a WLAN voice solution, the critical design element will be the wireless infrastructure we put in place to support those handsets. No one is going to be happy with their WLAN handset if they cannot use it to make a call.

Earlier we described the access points, controllers, antennas, protocols, and security mechanisms we use in WLANs, but now we have to examine how those elements must be modified to support voice. The original 802.11 wireless LAN protocols were designed to address the requirements of data users. Having all of the users vying or contending for the channel introduces transit delay and jitter, but for the most part, those issues are inconsequential for data users. The 802.11 Distributed Control Function is designed to treat all data users equally; when we support voice, we will need to treat some users better than others.

To address these and other voice requirements, the WLAN protocols are being modified to address real-time voice and video. The most important of those developments is the 802.11e standard for QoS. While QoS is the most obvious requirement, there are a number of steps that must be taken in the WLAN network design to address real-time voice and video. Those issues include security, load balancing, handoffs, and network management capabilities.

While some companies have deployed VoWLAN networks, most of...